The present invention relates generally to reducing CO2 emissions from exhaust gases. The exhaust gas can be produced by an energy plant, such as a coal plant or other power plant. It is beneficial to develop technologies for mitigating CO2 emissions from various sources that produce exhaust gases to reduce their contribution to the environment.
Membranes have attracted attention as a potential solution technology for various gas separation unit operations. However, there have been concerns about the practicality of membranes for capturing CO2 in this field. For example, the compression of flue/exhaust gas of approximately 10 bars (1×106 Pascals) or more is considered necessary when using membranes. The energy requirement and costs associated with the compression of such large volumes of flue/exhaust gas is a concern. Another concern is the need to compress a permeated CO2 gas, which is often considered a necessary step for successful sequestration of the CO2. The compression of the permeated CO2 gas can also impose an unaffordable energy burden on the industrial processes. Steam is often suggested as a sweep-gas to reduce the CO2 partial pressure on the permeate side of the membrane. It has been shown that the energy required to generate the sweep-gas is also cost-prohibitive. Accordingly, there is a need to address at least each of the above concerns with CO2 mitigation simultaneously in currently available membranes and when desiring to perform CO2 sequestration.